1. Field of the Invention
It is sometimes desirable to control the temperature of a zone in response to a fluctuant temperature of another zone, so that a condition of thermal equilibrium continually exists between the two. The same may be true of liquid or solid bodies. The temperature of the "lead" zone or body, that is, the one which is independently variable, may fluctuate as the result of a biological or chemical process such as a fermentation or exothermic reaction. Alternatively, it may be influenced by some electrical or mechanical device.
This invention relates to an electronic temperature equalizer which is designed to very precisely achieve the type of interzonal control just described. One application of the equalizer is demonstrated in an adiabatic reactor, wherein the temperature of the zone surrounding the reaction vessel is continually adjusted to correspond to that within the vessel. We have found such a system to be useful in studying storage damage in grain, whereby a laboratory model can be constructed for duplicating the conditions in the center of a bin. Among other things, it could also he utilized to minimize temperature gradients throughout a reaction or crystallization product.
2 Description of the Prior Art
Most prior art temperature controllers are designed to establish and maintain a predetermined temperature value and to thereafter hold it at that value within a prescribed tolerance. For example, in Dawson, U.S. Pat. No. 3,918,636, the objective is to maintain one or more bodies of water at a constant temperature as required for laboratory experimentation. The temperature is preset by means of a variable resistor in one arm of a Wheatstone bridge having a thermistor used as a sensor in another arm. In U.S. Pat. No. 3,563,460. Nine shows a system for maintaining stored grain at a predetermined temperature by activating a fan in response to heat generated by the grain. The control device employs the same Wheatstone bridge arrangement employed by Dawson.
It becomes eminently apparent from a review of the prior art that to devise a means for following a target temperature which is independently variable would require a basic departure from the conventional concepts heretofore known.